Polydentate ligands phosphines

By Addition ofP—H to Unsaturated Compounds. This route continues to be exploited for the synthesis of polydentate tertiary phosphine ligands. Thus base-catalysed addition of diphenylvinylphosphine to the secondary phosphine (25) affords (26).23 Neopentylpolytertiaryphosphines, e.g. (27), have been similarly prepared24 by addition of primary or secondary phosphines to vinylphosphines (or the related phosphine sulphides, followed by a desulphurization step). 

A large variety of polydentate ligands containing nitrogen and phosphorus can be prepared easily by the reaction of ethylenediamine or substituted ethyl-enediamines, formaldehyde, and secondary phosphines, as illustrated below. Furthermore, the scope of this reaction is very wide. It includes the compounds listed here and it is also general for amines which contain at least one N-—H bond and for phosphines which contain at least one P—H bond. 

The coordination chemistry of these and other polydentate tertiary phosphines has been documented with a variety of ligating modes observed for these ligands.214"216 Aspects of coordination behavior of the above polydentate phosphines with Fe,22, 225,231,232 Ru,233 Co,221... 

Preparation of Phosphines from Metallated Phosphines.- This route contines to find wide application. New polydentate ligands,... 

The metals which form square planar complexes belong to the Co(I), Ni(II), and Cu(III) triads. Although examples for each are known, the RW, Ir, Pd , Pt i, and Au form the most prevalent square planar complexes. Small linear or planar ligands are needed to achieve a close approach between molecules in a stack. Bulky ligands, for example, macroc lic polydentate ligands or substituted phosphines, amines, and sulfides, sterically hinder the close approach of molecules in a column. 

During the past ten years, two valuable alternatives to the Grignard and alkali-metal-organophosphide syntheses of tertiary phosphines have been developed. By choosing the appropriate route and reagents, one should now be able to tailor-make polydentate ligands to incorporate just about any electronic and/or steric effects desired. 

Early complexes developed by Lee and coworkers for use in Suzuki couplings were developed bearing various functionalities. Polydentate ligands involving a tethered NHC/phosphine or NHC/pyridine system were isolated, and their... 

A new cyclophosphazene carrying phosphine ligands (166) has been prepared from bis(2,2 -dioxy-l,P-biphenyl)dichlorocyclotriphosphazene and ort/io-diphenylphosphine-phenol, and has been used to form the Au(i) and Pt(ii) complexes (167-169) as shown by X-ray crystallography. The sequential reaction of the potentially polydentate ligand hexakis(2-pyridyloxy)cyclotriphos-phazene (OPy) with the anhydrous dichlorides M Cl2 and M Cl2 (M = Cu or Co, M = Co or Zn) gave the heteropolynuclear complexes (170-172),... 

Replacement of three C-substituents in phosphines by oxy groups produces triesters of phosphorous acid, also called phosphites. Such phosphites play a crucial role as mono- and bidentate ligands, but also as polydentate ligands, in numerous catalytic applications [1]. In Rh-catalyzed hydroformylation, they are indispensable in regioselective transformations at each scale. Several chiral phosphites based on rather complicated alcohols have also been designed for use in asymmetric hydroformylations [2]. 

---